Monday, June 30, 2014

The International Surface Temperature Initiative is pleased to release version 1 of a new monthly dataset that brings together new
and existing sources of surface air temperature. Users are provided a way to more
completely track the origin of surface air temperature data from its earliest
available source through its integration into a merged data holding. The data
are provided in various stages that lead to the integrated product. This release is the culmination of three years effort by an
international group of scientists to produce a truly comprehensive, open and
transparent set of fundamental monthly data holdings. The databank has been previously available in beta form, giving the public a chance to provide feedback. We have received numerous comments and have updated many of our sources. This release consists of:

Over 50 distinct sources, submitted to the databank to date in Stage 0 (hardcopy / image; where
available), Stage 1 (native digital format), and Stage 2 (converted to common
format and with provenance flags).

All code to convert the Stage 1 holdings to Stage 2.

A recommended merged product and several
variants which have all been built off the Stage 2 holdings. 2 ASCII formats are provided (ISTI format, GHCN format), along with a CF Compliant netCDF format.

All code used to process the data merge, along with statistical auxiliary files.

Documentation necessary to understand at a high
level the processing of the data, including the location of the manuscript published in Geoscience Data Journal.

The entire databank can be found here and the merged product is located here. Earlier betas are also found here. Because the databank is version controlled, we welcome any feedback. We will be providing updates on the blog regarding any new releases.

Saturday, June 28, 2014

Since records of surface temperature started being made
there have been iterations of the fixed points standards used by
national metrological institutes (that is not a typo). Assuming that all
meteorological measurements through time have been made to such
standards (which may be a considerable stretch) this would have imparted
changes to the records that are not physical in origin. As part of meteomet
efforts have been made to understand this. It is a relatively small
effect compared to effects of other long recognized data issues. Nevertheless it is important to properly and systematically consider all
sources of potential biases as exhaustively as possible.

Temperature
is one of the main quantities measured in meteorology and plays a key
role in weather forecasts and climate determination. The instrumental
temperature recordings now spans well over a century, with some records
extending back to the 17th century, and represents an invaluable tool in
evaluating historic climatic trends. However, ensuring the quality of
the data records is challenging, with issues arising from the wide range
of sensors used, how the sensors were calibrated, and how the data was
recorded and written down. In particular, the very definition of the
temperature scales have evolved. While they have always been based on
calibration of instruments via a series of material phase transitions
(fixed points), the evolution of sensors, measuring techniques and
revisions of the fixed points used has introduced differences that may
lead to difficulties when studying historic temperature records. The
conversion program here presented deals with this issue for 20th century
data by implementing a proposed mathematical model to allow the
conversion from historical scales to the currently adopted International
Temperature Scale of 1990 (ITS-90). This program can convert large
files of historical records to the current international temperature
scale, a feature which is intended to help in the harmonisation
processes of long historic series. This work is part of the project
“MeteoMet” funded by the EURAMET, the European association of National
Institutes of Metrology, and is part of a major general effort in
identifying the several sources of uncertainty in climate and
meteorological records.

Michael de Podesta, who has served on the steering committee since ISTI's inception, reviewed the software for ISTI and had the following summary:

Assuming
that calibration procedures immediately spread throughout the world –
homogenisation algorithms might conceivably see adjustments in 1968,
with smaller adjustments in 1990.If
undetected, the effect would be to create a bias in the temperature
record. This is difficult to calculate since the bias is temperature
dependent, but if the mean land-surface temperature is ~10°C and if
temperature excursions are typically ±10 °C then one might expect that
the effect to be that records prior to 1968 were systematically
overestimated by about 0.005 °C, and records between 1968 and 1990 by
about 0.003 °C.

Michael's full summary which includes some graphical and tabular summaries can be found here.

The code package is a windows operating system based package. It is available here.

Wednesday, June 4, 2014

Just briefly to note that a discussion paper is now open for comment authored by the members of the benchmarking working group. This paper discusses the concepts and frameworks that will underpin all aspects of the benchmarking and assessment exercise. Its open to review until July 30th. Please do, if you have time and inclination, pop along and have a read and provide a constructive (!) review. The discussion site is at http://www.geosci-instrum-method-data-syst-discuss.net/4/235/2014/gid-4-235-2014.html .

Also, watch this space at the end of this month for exciting developments on the first pillar of the ISTI framework - the databank.

Finally, we are rapidly hurtling towards the SAMSI/IMAGe/ISTI workshop on surface temperatures and their analyses. Its going to be a busy few weeks so expect this blog to be somewhat less moribund than of late ...